This invention relates to power management within the context of wireless ad-hoc networks. More specifically, the invention relates to a power management scheme configured to reduce power consumption and enhance data throughput in wireless ad-hoc networks.
Wireless communication between mobile nodes has become increasingly popular. There are essentially two techniques used for linking nodes in wireless networks. The first uses existing cellular networks, which are essentially systems of repeaters wherein the transmitting or originating node contacts a repeater and the repeater retransmits the signal to allow for reception at the destination node. The obvious drawbacks to the cellular systems include significant infrastructure costs and geographic limitations. Because of the significant infrastructure costs it is not practical to have cellular networks in all areas. Furthermore, in times of emergency, such as earthquake, fire, or power interruption the cellular network can become disabled in the precise location where it is needed most.
The second technique for linking nodes is to form a wireless ad-hoc network among all users within a limited geographical region. In this situation each user participating in the ad-hoc network should be capable of, and willing to, forward data packets and participate in ascertaining if the packet was delivered from the original source to the final destination. The wireless ad-hoc network has a number of advantages over cellular networks. First, the wireless ad-hoc network is more robust, in that it does not depend on a single node, but rather has a number of redundant, fault tolerant, nodes, each of which can replace or augment its nearest neighbor. Additionally, the ad-hoc network can change position and shape in real time.
Various routing algorithms have been proposed for wireless ad-hoc networks in the literature. These algorithms are mainly focused on establishing routes and maintaining these routes under frequent and unpredictable connectivity changes. The implicit assumption in most of the earlier work on routing protocols is that nodes"" transmit powers are fixed. Power control is known in the context of cellular systems and satellite systems. Thus one drawback of the versatile ad-hoc network is power consumption. Conventional wireless ad-hoc networks have nodes that generally transmit at a single power level, regardless of the distance that the signal will traverse. Transmitting with too much power is costly in terms of node resources and can cause unwanted interference to nodes engaged in reception of other signals. Thus it would be desirable to have a power management scheme that reduces power consumption, enhances data throughput, and reduces demand for node resources traditionally allocated for data reception and transmission.
It is an object of the present invention is to provide both a method and apparatus configured to reduce power consumption, enhance data throughput, and reduce demand for node resources traditionally allocated for data reception and transmission.
Power based connectivity provides improved end-to-end network throughput, and simultaneously reduces power consumption. In wireless ad-hoc networks, as nodal transmitted power increases, the connectivity range also increases, consequently each node in the wireless ad-hoc network would reach almost all other nodes in a single hop. However, since higher powers cause higher interference levels, more collisions are likely to occur. By reducing the transmission power levels at each node such that the node can directly connect to only a small subset of nodes in the network, the interference zones may be significantly reduced.
The method and apparatus according to the present invention provides a system that dynamically reaches a near-optimal operating power level in a wireless ad-hoc network, such that the end-to-end throughput is optimized. In addition to optimizing end-to-end throughput the present invention permits a reduction in the total power usage. One of the major advantages provided by the present invention is conservation of power. Power is a particularly precious resource in the wireless environment. Typical wireless ad-hoc networks that might benefit from power based routing include low mobility wireless ad-hoc networks, including pedestrian networks formed by soldiers relaying situational awareness information on the battlefield, rescue workers and emergency disaster relief workers. The invention may also find application in a variety of sensor networks. Another object of the present invention is to provide a power management scheme that reduces power consumption, increases transmission range, enhances data throughput, and reduces demand for node resources traditionally allocated for data reception and transmission. The wireless ad-hoc network of the present invention uses only the minimum power required to contact a limited number of the nearest nodes, and consequently minimizes power requirements because transmission power requirements are reduced. Furthermore, transmission range can be greater than that found in a network where the signals are not relayed.